-fsource-location placed a trace_stment() call before the start of the generated
C for every COBOL instruction.  This was needed to make the .loc assembly directives
work.  Simon replaced those calls with "call cob_nop()".  I get rid of them, except
when the following .loc statement has "discriminator" in it.  Otherwise the code
doesn't trap properly through some loops.  I have no idea why.